This thesis is the result of a 4-year collaboration between the Technical University of Munich and the BMW Group.
The goal was to apply substructuring methods to the Noise Vibration Harshness (NVH) engineering needed for integrating electric climate compressors in upcoming vehicles.
The compressor is one of the major contributors to the cabin noise in battery electric vehicles (BEVs).
An accurate yet practical development process for its vehicle integration is crucial for industry.
Specifically, the aim was to simulate the compressor noise in the cabin for different, virtual design variants of the isolation concept.
Therefore, the methods from two broader fields were applied:
First, the excitation of the compressor was modeled with component transfer path analysis (TPA) methods.
Second, the full transfer path from the compressor to the driver's ear is assembled from multiple subcomponent models, via dynamic substructuring (DS).
For accomplishing the above-mentioned goals, different gaps in the current technology have been identified, which will be addressed in this thesis.
With frequency-based substructuring (FBS), a subclass of DS, it is possible to couple experimental and numerical substructure models in a virtual assembly.
For the compressor, it was found that including rigid body models in the transfer path is a valuable addition.
The proper formulation and integration of rigid body models in the framework of FBS will be presented.
Another bottleneck at the onset of this project, was the proper modeling of rubber bushings in the transfer path.
A novel method for experimentally identifying accurate substructure models of rubber isolators was developed.
The rotating components in the compressor introduce gyroscopic effects that influence its dynamics.
A novel substructuring method for virtually coupling gyroscopic terms to a component could prove that these effects are not relevant for the compressor case.
The compressor's excitation is described by blocked forces.
Applying the blocked forces to the substructured transfer path of the assembly allows to simulate the sound in a virtual prototype.
One goal was to make the simulated results audible to non-acoustic experts, which required the creation of sound files.
This allowed for a subjective comparison of different designs at an early development stage.
Since the noise predictions with TPA are typically in the frequency domain, some signal processing is required to create sound files in the time domain.
Different methods for auralization will be compared, which could not be found in the existing TPA literature.
Due to the inverse process for identifying the blocked forces, measurement noise can be amplified to unacceptably high levels, which are audible in the sound predictions.
Regularization methods have the potential to significantly suppress the noise amplification, which is explained and exemplified for blocked force TPA.
Additionally, it was found that only the structure-borne sound transmission was not sufficient to describe the compressor noise in the cabin.
The compressor is also directly radiating air-borne sound from its housing, which will be included in the NVH model by means of equivalent monopoles.
The application examples at the thesis' end are extending the current state-of-the-art, by showing how the modular vehicle models can be used for early phase, parametric design optimizations on a complex NVH problem.
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